Horizontal reactor for the vapor phase polymerization of monomers

ABSTRACT

Apparatus for the vapor phase polymerization of at least one polymerizable monomer comprising: 
     (a) a horizontal, stirred reactor of substantially circular cross section containing a centrally-located drive shaft extending longitudinally through said reactor to which are attached a plurality of adjacently located paddles, which paddles cause essentially no forward or backward movement of the particulate matter contained in said reactor and extend transversely within and to a short distance from the internal surfaces of said reactor, said reactor being divided into two or more individually polymerization-temperature controllable polymerization sections by one or more barriers constructed to allow free gas mixing within said reactor and control particulate movement between said sections; 
     (b) driving means for said drive shaft; 
     (c) one or more outlets for removal of reactor off-gases situated along the topward part of said reactor; 
     (d) one or more vapor recycle inlets situated along the bottomward portion of said reactor for the introduction of said at least one monomer; 
     (e) one or more catalyst addition inlets situated along said reactor; 
     (f) a plurality of quench liquid inlets situated along the topward part of said reactor whereby quench liquid may be introduced into said polymerization sections of said reactor; and 
     (g) a particulate matter take-off at one end of said reactor.

This is a division, of application Ser. No. 642,583, filed 12-19-75which is a continuation of Appl. Ser. No. 533,020 now abandoned, filed12-16-74.

SUMMARY OF THE INVENTION

This invention relates to novel apparatus for the vapor statepolymerization of a polymerizable monomer or mixture thereof to producenormally solid polymeric substances and, more specifically, relates toapparatus for the polymerization of said monomer or mixture from thevapor state by an essentially isobaric process using a high yieldcatalyst and, optionally, cocatalyst, which apparatus is a horizontal,quench-cooled, stirred-bed reactor utilizing essentially total reactoroff-gas recycle.

In accordance with the instant invention a reactor is disclosed whichcan economically and efficiently convert a polymerizable monomer or amixture thereof to polymeric substances in a vapor phase, essentiallyisobaric polymerization process, which reactor is a stirred-bed,quench-cooled, horizontal reactor with essentially total reactor off-gasrecycle capable of multiple temperature operation. The apparatus ischaracterized by a stirred agitation of the subfluidized polymer bedcontained therein by transversely oriented paddles connected to alongitudinally oriented drive shaft typically located centrally in thereactor and is further characterized by segmentation of the reactor intoone or more polymerization sections separated one from another bysuitable barriers such as weirs, such sections capable of beingindividually controlled with respect to polymer production rates andpolymerization temperatures and, in one embodiment, partial pressures ofthe reactor gases as well.

BACKGROUND OF THE INVENTION

One of the problems in solution or slurry polymerization of monomers isthe capital costs required in the production thereof. Monomerpolymerization using a vapor phase process can be considerably moreeconomical if certain problems inherent in vapor state polymerizationcan be solved. These include problems of carrying out the polymerizationin a thermally controlled fashion so as to avoid hot spots, maintaininga proper product particle size distribution and, in the case wherecatalysts are utilized which have extremely high yields but areextremely sensitive to poisoning, decreasing to a minimum the amount ofmake-up material seen by the catalyst per amount of product formed.Another problem related to certain catalyst combinations is the narrowmolecular weight distribution of the products formed with thesecatalysts. Now we have discovered a vapor phase reactor which largely orcompletely solves the above referred to problems and reaps importanteconomic benefits through savings in energy consumption, raw materialsand capital costs.

In U.S. Pat. No. 2,502,953 (Jahnig) a weired, downwardly orientedapparatus for contacting, fluidized solid particles with gaseous fluidsto purge or strip volatiles from such solids is taught.

In U.S. Pat. No. 2,936,303 (Goins) a vapor state polymerization ofethylene, propylene or mixtures thereof is carried out in acountercurrent, fluidized bed in the presence of inert diluent gas. Inthe process described therein catalyst in solid form is passeddownwardly in the reactor and, for example, ethylene mixed with diluentgas is passed countercurrently up through a series of vertical fluidizedbed reaction zones. In this process the reaction in the various reactionzones can be controlled independently by taking off-gas from the lastreaction zone, cooling it, and recycling portions of such off-gases toeach of the reaction zones. However, because of the use of diluent gasand a fluidized bed large quantities of gas must be passed through thereactor per unit of polymer produced.

In U.S. Pat. No. 3,023,203 (Dye) a suspended, gas phase polymerizationof olefins using a reactor having three concentric superimposed verticalsections, comminuted catalyst addition suspended in the entering gas,and temperature regulation by gas cooling is shown. The process includespolymer removal without pressure letdown.

In U.S. Pat. No. 3,254,070 (Roelen) a method for the gas phasepolymerization of ethylene using conventional cooling is describedwherein a mixture of reaction products and solid or liquid catalysts isconstantly being mechanically subdivided. This patent additionallyteaches that the reacting material may be agitatingly moved through anumber of stages each with different polymerization conditions. Anadditional mode described therein teaches that the first few stages maybe carried out using liquid phase polymerization finishing up withpolymerization in the vapor phase. Different polymerization temperaturesmay be used in the separate reactors.

In U.S. Pat. No. 3,256,263 (Wisseroth et al.) a method of removing heatand producing intensive movement of the polymeric product producedduring the gas phase polymerization of olefins in a stirred, vertical,fluidized reactor is described using mechanical agitation andintroduction of the polymerization monomer immediately after expansivecooling in the form of moving gas or liquid jets.

In U.S. Pat. No. 3,300,457 (Schmid et al.) polymerization ofmonoolefins, particularly ethylene and propylene, is accomplished in afluidized bed using a stirred, vertical reactor. Catalysts and polymerin the reactor are moved in the direction of flow of the monoolefin bythe stirring and heat is removed by cooling the walls of the vessel, byconduction using the gas stream, or by the introduction of liquefiedmonoolefin.

In U.S. Pat. No. 3,469,948 (Anderson et al.) a horizontal paddle typepolymerization reactor using pulsed purge gases including thepolymerizable olefin is described. The teaching of this patent isdirected to the use of longitudinal paddles which are suitably shaped togive forward movement to the solid polymer resulting from the vaporphase polymerization.

In U.S. Pat. No. 3,652,527 (Trieschmann et al.) a process for the gasphase polymerization of propylene in a stirred-bed, vertical reactorusing evaporative cooling of the reaction is described. This patentteaches that it is essential that one component of the catalystcombination must be directly placed on the bed of solid polymer producedin the polymerization and the second catalyst component must beintroduced in the gas phase above the bed.

Finally, in British Pat. No. 1,354,020 (Badische) a vapor phase olefinpolymerization process is described in which the heat generated in thepolymerization process is removed by the introduction of the monomer andheat transfer agents in gaseous or liquid state in the polymerizationzone. However, the use of multiple polymerization temperature in thevertical, stirred, fluid-bed reactor is not taught and it is difficultto see how such individual control could be accomplished in theapparatus described.

SHORT DESCRIPTION OF THE DRAWING

FIG. 1 shows a longitudinal view of one embodiment of the reactordescribed herein.

FIG. 2 shows a transverse view of such reactor along line 2--2 of FIG.1.

FIG. 3 shows a second transverse view of the reactor of FIG. 1 alongline 3--3 of FIG. 1.

FIG. 4 shows one embodiment of an essentially isobaric process by whichthe reactor described herein is employed with essentially total reactoroff-gas recycled.

STATEMENT OF THE INVENTION

The invention described herein is a horizontal reactor for theessentially isobaric, vapor phase polymerization of polymerizablemonomers utilizing essentially total reactor off-gas recycle and aquench-cooled, stirred-bed mode of operation. It is particularly adaptedfor use with polymerization catalysts which have a high enoughpolymerization yield that catalyst residues need not be removed from thepolymeric product during the polymer finishing process. In general, thereactor utilizes a controlled introduction of catalyst components andquench liquid into its two or more polymerization sections directly ontoand into the stirred, subfluidized bed of forming polymer andpolymerization of monomer from the vapor phase in and over such bed. Thepolymer solid is continuously removed by passing through a take-offbarrier generally at one end of the reactor into a take-off vessel. Thereactor introduces monomer or a mixture thereof and, optionally,hydrogen largely or wholly underneath the polymer bed and quench liquidonto the surface of the bed. The reactor generally has two or morepolymerization sections and the several sections are separated from eachother by weirs or other suitably shaped barriers to prevent grossback-mixing between sections. Each section may be individuallycontrolled in terms of polymerization temperature and polymer productionrate so that a polymeric product having a controlled spread of molecularweight and particle size may more easily be produced.

Reactor off-gases are removed along the top of the reactor afterremoving entrained polymer fines as completely as possible from theoff-gases. The reactor off-gases are then taken to a separation zonewhereby the quench liquid is at least in part separated along with anyfurther polymer fines and some of the catalyst components frompolymerization monomer and hydrogen, if used, which monomer and hydrogenare then recycled to inlets spaced along the various polymerizationsections of the reactor and located largely or wholly underneath thesurface of the polymer bed. A portion of the quench liquid including thefurther polymer fines is taken off the separation zone and in major partreturned to inlets spaced along the top of the reactor. A minor part ofsuch quench liquid purified of polymer fines and catalyst components isfed into a catalyst make-up zone for catalyst diluent so that freshquench liquid need not be introduced for that purpose. Provision may bemade in the multiple section reactor to introduce the catalystcomponents and quench liquid at different rates into the differentsections of the reactor to aid in individual control of thepolymerization temperatures and polymer production rates of the varioussections. Catalyst components may be added into or onto the stirred bed.

By the term vapor state reactor or process is meant a reactor orprocess, the monomer or monomers of which are vapors or gases under theconditions prevailing in the reactor.

The recycle system and reactor are so designed that they operateessentially isobarically. That is more than the normal operatingvariations are present. Preferably, the reactor and recycle systempressure variations are no more than ± 25 psig and, more preferably, nomore than ± 10 psig.

One embodiment of a process using the reactor of this invention is shownin detail in FIG. 4 which Figure may be divided roughly into two areas,the reactor area and the reactor off-gas treatment (separation) andcatalyst make-up area.

As may be seen by looking at FIG. 4 the reactor volume of horizontalpolymerization reactor 401 is divided into several stirringly agitatedsections 467, 469, 471 and 473 to provide for the possibility ofoperating the different sections of reactor at different temperaturesand/or different polymer production rates. Polymerization takes place ineach of the aforementioned sections to form a polymer bed distributedthroughout the reactor and the polymerization temperature of each of thesections may be individually controlled by a combination of methodsincluding the stirring agitation, the controlled differentialintroduction of vapor recycle into each of the sections through inlets475, 477, 479 and 481 spaced along the bottom of the reactor, and theintroduction into each of the sections of inert quench liquid andcatalyst components at different rates through quench liquid inlets 453,455, 457 and 459 and catalyst inlets 423, 425, 427 and 429 spaced alongthe top of the reactor.

Reactor off-gases are removed through outlets 483, 485, 487, and 489.Since a certain deleterious amount of polymer fines may be produced inthe reactor they advantageously are substantially removed prior totransfer of the reactor off-gases to the reactor off-gas treatment andcatalyst make-up area by using traps, filters, settlers, cyclones orscrubbers or a combination thereof.

Polymer solid is produced in each of the stirringly agitated sections467 through 473 and, due to the continued production of such polymer, anamount of product constantly passes through the take-off barrier and outof the reactor into polymer take-off vessel 403.

Catalyst, dissolved or slurried in recycle quench liquid, isadvantageously introduced onto the surface of the bed in at least one ofthe various polymerization reaction sections through inlets 423, 425,427, and 429. Similarly placed inlets 453, 455, 457, and 459 are used tointroduce the recycle quench liquid, which may contain cocatalyst, ontothe be in the individual reaction sections. However, depending on thenature of the catalyst, cocatalyst and monomer to be polymerized,catalyst and/or cocatalyst can be sprayed or otherwise introduced intothe reactor neat or in other non-polymerizable vehicles. Alternatively,for some monomers, catalyst and cocatalyst can be added to make-up zone445 and together added to reactor 401.

In one mode of operation it has been found advantageous to make thecatalyst and quench liquid inlets concentric so that the catalyst andquench liquid are sprayed into the reactor and onto the surface of thepolymer bed in such a way as to more evenly distribute the catalysts onthe polymer bed surface. However, the catalyst and quench inlets may bemade separate and the catalysts and quench liquid introduced separatelyonto the bed.

The reactor off-gases are taken via line 431 to scrubber tower 433wherein at least part of the quench liquid component of the off-gases,further polymer fines and some of catalyst components are removed fromthe polymerizable monomer and hydrogen, if used. The polymerizablemonomer and hydrogen together with some quench liquid vapor are returnedto reactor 401 from the top of scrubber tower 433, after,advantageously, passing through heat exchanger 460 and separator 461 tocondense out additional quench liquid, via blower 444 and vapor recycleline 456 with additional hydrogen and monomer make-up being added vialines 463 and 465. Alternatively, monomer and hydrogen can be returnedfrom scrubber tower 433 to reactor 401 bypassing heat exchanger 460 andseparator 461. The amount of vapor recycle introduced into theindividual sections of the reactor via inlets 475, 477, 479, and 481 canbe individually controlled by valves 491, 493, 495, and 497 and the bedthereby kept in a subfluidized state. The quench liquid of separator 461is essentially free of polymer fines and catalyst components andsuitable for use in catalyst make-up zone 445.

Quench liquid, separated from the reactor off-gases, is cooled by heatexchanger 454 and returned in major portion to the top of scrubber tower433 via line 438. A minor portion of the quench liquid is returnedthrough line 437, heat exchanger 443, pump 438 and quench liquid recycleline 451 to quench liquid inlets 453, 455, 457, and 459 carrying with itsome monomer, hydrogen, cocatalyst and any polymer fines carried by theoff-gases into scrubber tower 433. Quench liquid make-up may be addedvia line 440. In the important embodiment in which cocatalyst is used,make-up cocatalyst may be added to catalyst make-up zone 445, injecteddirectly into the recycle quench liquid stream through line 447 or maybe added directly in a non-polymerizable vehicle into reactor 401. Asmall portion of quench liquid essentially free of polymer fines andcatalyst components is taken off separator 461 and passed through line434 and pump 436 to catalyst make-up zone 445 for catalyst make-uppurposes.

Polymerization in catalyst make-up zone 445 or associated line 449 andinlets 423-429 can cause serious plugging problems and may be controlledby keeping the cocatalyst concentration in catalyst make-up zone 445below a certain value, which value depends upon the identity of thecatalyst and cocatalyst used and the monomer to be polymerized. Wheremake-up cocatalyst is added to catalyst make-up zone 445 provision mayhave to be made to prevent polymerization from occurring in associatedlines by cooling the make-up zone, decreasing the residence time of thecatalyst components therein, etc. Alternatively, make-up quench liquidfrom line 447 can be used in catalyst make-up zone 445 in place ofrecycle quench liquid to prevent polymerization of monomer in said zone.

Valve 499 has been provided in the catalyst make-up zone bypass line inorder to more easily vary the concentration of catalyst in the catalystmake-up introduced into the reactor. It has been found that the particlesize of the polymer produced in reactor 401 can be advantageously variedby varying the concentration of the catalyst being introduced throughinlets 423, 425, 427 and 429. Further, it has been found advantageous tovary the catalyst concentration either by changing its concentration inmake-up zone 445 or, additionally and alternatively, to change itsconcentration by introducing quench liquid into catalyst line 449 viavalve 499 just prior to the point where the catalyst enters the catalystinlets 423, 425, 427, and 429. Make-up catalyst is added through line442.

The polymer solid which builds up in stirred reactor 401 traverses thelength of reactor essentially because of polymer build-up in the reactorbed and not by the stirring agitation. This condition is insured by thepaddle design used which provides for agitation but not for backward orforward movement of the bed. Polymer particles in the bed adjacent tothe take-off barrier are swept by the stirring through the take-offbarrier opening, which opening may be made variable in size and positionby a number of devices for maintaining different levels of polymer solidin the reactor.

Weirs, if used, may be attached to drive shaft 404 with slip rings orfixed to the walls of the reactor and are beneficially oriented so thatthe top of the weir is roughly aligned with the bed orientation duringagitation. This provides for spill-over along the entire length of theweir top. However, the weirs can be oriented horizontally, if desired.Other types of barriers may be used in place of the wiers to preventgross back-mixing between the two or more sections of the reactor. Forexample, thin wall barriers attached to drive shaft 404 which fill thereactor cross-section and have one or more holes cut in them may be usedas can be understood by one skilled in the art.

The polymer particles passing through such take-off barrier opening fallinto polymer take-off vessel 403. The polymer solid taken off can betreated with additives and melt extruded in the ways conventional to theart or it can be taken off without substantial pressure letdown in sucha way that the solid is melted in vessel 403 and the resulting moltenpolymer treated with kill substance and additives and devolatilizedwhile still in the molten state and then finished into commerciallysized product by conventional techniques.

FIG. 1 shows in detail reactor 401 of FIG. 4. It may be seen that theinterior of reactor 101 is composed of four individually controllablepolymerization sections 167 to 173 separated from one another by weirs110 to 114, which weirs extend upwardly to somewhat over the middle ofthe reactor and are oriented so that their top surfaces line upapproximately with the polymer bed surface during agitation. In afavored embodiment weirs 110, 112 and 114 are constructed in height sothat the polymer bed fills about half the volume of the reactor. As thesolid polymer exceeds the weir height it falls into the adjacent sectionmoving in the direction of the take-off.

In a mode wherein it is desired to operate with two or more gascompositions (different hydrogen concentrations) as well as differentsection temperatures, all the section barriers are constructed as aboveexcept for the one or more dividing structures which divide the reactorinto the compartments of different gas compositions. The dividingstructures are thin wall barriers extending upwardly and filling thecross-section of the reactor and contain an opening situated beneath thelevel of the polymer bed for polymer solid movement. Gas intermixingbetween the compartments is thereby be controlled. Operating in such avariable gas composition mode, the individual compartments should haveseparate reactor off-gas recycle treatments and returns and may haveseparate hydrogen and monomer make-ups.

Generally, the dividing structures are designed to prevent extensiveintermixing of the vapors between the individual compartments, howeverin one mode of multiple hydrogen operation the vapors are deliberatelymixed by feeding the vapors from the hydrogen poor compartment to thehydrogen rich compartment and adding make-up monomer primarily to thehydrogen poor compartment and hydrogen make-up primarily to the hydrogenrich compartment.

The interior of the reactor is equipped with a rotating paddle driveshaft 104 extending longitudinally through reactor 101 to which areattached paddles extending transversely from the shaft and making closeclearance with the inside wall of reactor 101 to insure adequate bedmixing at the reactor wall. The paddles are preferably flat to maximizebed agitation for a given rotational speed and preferably two paddlesper impellor are used. The width of the paddles is such that betweenabout four and about twelve impellors (8 to 24 paddles) will be presentin a reactor section of about three feet in length. The orientation ofthe paddles on adjacent impellors is about ninety degrees. The paddlesare so constructed to minimize any forward or backward movement of thebed during stirring and are driven by motor 102 at such a speed as togive a slow and regular turnover of the entire polymer bed contained inthe reactor. The speed at which the impellors turn should be fast enoughto provide the desired heat and mass transfer between liquid, solid andgas but no so fast that the finer portions of the polymer bed are thrownup in large quantities into the space above the bed. That is, the speedtypically is about 5 to about 30 RPM so that the integrity of the bed ismaintained.

The space following the take-off barrier and above the take-off vesselis likewise equipped with one or more similar impellors, 120, the numberof which depend upon the size of the take-off. However, take-offassemblies such as end or side take-off apertures, which assembliesreplace the take-off barrier, may be used as can be understood by oneskilled in the art.

A plurality of catalyst and quench inlets can be used in reactor 101 andone or more pairs of catalyst and quench inlets may be used for eachreactor section, 167 to 173. The catalyst and quench inlets aretypically designed so that the catalyst and quench liquid aredistributed onto the top of the agitated bed at roughly the samelocation. Such introduction of catalyst and quench liquid combined withslow agitation has been found to provide more uniform polymerization andprevent localized fusion in the polymer bed and hence reduce the numberof molten plugs of polymer formed and give more trouble free performanceof the reactor. It is advantageous in one mode of carrying outpolymerization in the reactor to provide for separately controlledaddition of catalyst components and quench liquid into the varioussections by means of, for example, valves. Such separately controlledadditions into reactor sections 167 to 173 help provide for separatecontrol of polymerization temperatures and polymer production rate amongthe sections and can be used to vary and control the molecular weightand particle size distribution of the polymer.

The vapor recycle which includes the polymerizable monomer or monomersand hydrogen, if used, is brought in through vapor recycle line 156 tovapor recycle inlets 175 to 181 at a rate designed to preventfluidization of the bed. The rate at which the vapor recycle gases areintroduced into the individual sections 167 to 173 can be controlled byvalves 191 to 197 and such control may be used to help vary the sectionpolymerization temperatures and polymer production rates if desired.

In an important embodiment of the process using the reactor describedherein in which the polymerization temperature of one or more of thesections is held at a different value than in the other section orsections (dual temperature operation or multi-temprature operation), itis advantageous to vary the concentrations of any or all of the catalystcomponents being introduced into the various sections. Particle sizedistribution and molecular weight distribution are advantageouslyaffected thereby. This may be accomplished by feeding the catalystinlets of the different sections individually. Even in singletemperature operation, it can be advantageous to feed one or more of thesections with catalyst components at a different concentrations thancatalyst components being introduced into the other section or sections.

The overall reactor temperature range for polymerization depends uponthe particular monomer which is being polymerized and the commercialproduct desired therefrom and as such are well known to those skilled inthis art. In general, the temperature range used varies between about40° C up to about the softening temperature of the bed. The totalpolymerization pressure is composed of the polymerizable monomerpressure, vaporized quench liquid pressure and hydrogen pressure, ifused, and such total pressure typically may vary from above aboutatmospheric to about 600 psig. The individual partial pressures of thecomponents making up the total pressure determine the rate at whichpolymerization occurs, the molecular weight, and the molecular weightdistribution of the polymer to be produced. The temperature ofpolymerization is controlled as may be understood by one skilled in theart.

False end plates inserted in reactor 101 for mechanical constructionpurposes are shown as 124 and 126.

In FIG. 2 a view of reactor 101 of FIG. 1 is shown along line 2--2 ofFIG. 1. The Figure shows the ninety degree orientation of the paddles onadjacent impellors, the adjustable take-off barrier opening 218 andtake-off barrier 216. Further, the Figure shows the orientation of weir214 and the polymer bed in reactor 201 and the direction of paddlemovement with respect to the bed orientation.

FIG. 3 shows a view of reactor 101 of FIG. 1 along line 3--3 of FIG. 1.Also shown are take-off barrier 316, its opening 318 and the directionof motion of the paddles with respect to take-off barrier opening 318and the orientation of the polymer bed.

The apparatus and process described herein may be applied to thepolymerization of polymerizable monomers which are polymerizable belowthe softening point of their polymeric forms including ethene, propene,4-methyl-pentene-1, butene-1, vinyl chloride, butadienes, styrene,poly(ethyleneterephthalate and mixtures of such monomers. Particularlysuitable are the polymerization of ethylene and propene.

The quench liquid used for temperature control is a readilyvolatilizable liquid which can be sprayed onto the surface of thepolymer bed to evaporatively conduit heat away from the polymer bed andthus must be inert to the monomer being polymerized, the catalystcomponents used in the polymerization, and have as high a heat ofevaporation as is consistent with ready volatilization of the quenchliquid in the reactor at the polymerization temperature. In generalalkanes such as propane, a butane, a pentane, or a hexane or closelyboiling mixtures thereof may be used. The preferred quench liquid forethene is isobutane or isopentane. It should be understood that wherethe monomer to be polymerized is readily condensible, e.g. propene, thequench liquid can be liquified monomer or a mixture of liquified monomerand an additional quench liquid.

The rate of quench liquid addition should be low enough to keep thepolymer bed dry, i.e. maintain the partial pressure of the quench liquidvapor below the dew point, yet large enough to obtain the maximumcooling effect of the quench liquid. Generally, the quench liquid willcarry away fifty percent or more of the heat of polymerization. Forpropene polymerization over ninety percent of the heat of polymerizationis desirably removed by the quench liquid. At a 200° F polymerizationtemperature in the polymerization of ethane, desirably more than seventypercent of the heat of polymerization is removed using isobutane andmore than 50 percent of the heat is removed using isopentane.

In general, the catalysts which are most useful to the process describedherein are those which are very active and give a high yield oncatalyst. Included in this group are cocatalysts composed oforganometallic compounds of Periodic Groups IA, IIA and IIIA andcatalysts which are based on transition metal compounds. Aluminum alkylcompound cocatalysts are especially preferred and ma be atrialkylaluminum or an alkyl aluminum halide such as a dialkyaluminumchloride. The transition metal catalyst can be a metal compound of GroupIV of Group V such as a titanium or vanadium compound, a compound ofGroup VI such as chromium or molybdenum oxide or may be one of the abovecatalysts supported on a magnesium-based support or a support such asalumina, silica, or silicaalumina.

The preferred catalysts and cocatalysts are as aforesaid high yieldcatalysts. By high yield is meant catalysts and cocatalysts the residuesof which do not have to be removed from the products of the process.

The preferred catalysts and cocatalysts for ethene polymerization are atrialkylaluminum cocatalyst with a catalyst which is a titanium compoundsupported on magnesium-based support or chromium oxide supported onalumina, silica or combinations thereof. For propene polymerization itis preferable to use a dialkylaluminum chloride cocatalyst and acatalyst which is an active titanium trichloride. However, the processand apparatus described herein are not meant to be limited to thecatalyst and cocatalyst used except in that the apparatus and processoperate best using high yield catalysts.

While the invention is described in connection with the specificExamples below, it is to be understood that these are for illustrativepurposes only. Many alternatives, modifications, and variations will beapparent to those skilled in the art and such alternatives,modifications and variations fall within the spirit and scope of theappended claims.

EXAMPLE I

A supported titanium chloride catalyst was suspended in isopentane at aconcentration of 30 milligrams/liter and pumped continuously to thereactor at a rate of 300 milliliters/hour. Aluminum triethyl dilutedwith isopentane to 1000 milligrams/liter was pumped continuously at arate to maintain the desired weight ratio of aluminum triethyl/catalyst,3/1 to 15/1. Ethylene was charged continuously at the rate ofpolymerization to maintain pressure, 300 psig. A continuous stream ofgas, 0.3 cubic feet/hour, was removed from the reactor for gaschromatographic analysis to maintain the hydrogen concentration in thereactor at 34 mol percent by intermittent hydrogen addition for polymermolecular weight control. The reactor polymer bed temperature was heldat 160° F. by continuously spraying isopentane at the appropriate rateonto the 30 R.P.M. stirred polymer bed. The vaporized isopentane wascondensed and recycled. The non-condensed gas (40° to 50° F.) wascontinuously recycled back into the bottom of the stirred polymer bed.The polymer bed level was maintained by the opening position in theretaining weir. The polymer overflow spilled out into the melter whichwas maintained at 350° to 400° F. by a combination of polymerizationheat and external electrical heat. The melted polymer sumped to thebottom and was forced through a horizontal piece of 3/4 inch diameter ×4 foot long pipe at 400° to 500° F. by the reactor pressure. Water wasinjected continuously into the polymer melt between the melter andcatalyst deactivator at a rate of 10 milliliters/hour. Polymer meltextruded from the catalyst deactivator through a 3/8 inch diameteropening and is drawn through a water bath and chopped. Polymer wasproduced at the rate of 1 to 3 pounds/hour at a yield level of 100,000grams polymer/gram catalyst. Physical properties of the polymer takenout of the melter are shown below in Table I and some properties of thepolymer powder taken from the reactor are shown in Table II.

                                      TABLE I                                     __________________________________________________________________________    Conditions:                                                                   160° F, 300 psig, 34 mol percent H.sub.2, 13/1 to 15/1 triethyl        aluminum/catalyst weight ratio                                                __________________________________________________________________________    General Properties           Run A   Run B.sup.(1)                            __________________________________________________________________________    Unanealed density, grams/cubic centimeter                                                                  0.961   0.959                                    Annealed density, grams/cubic centimeter                                                                   0.977   0.977                                    Inherent viscosity, dl/gram  1.87    2.29                                     Melt index, MF.sub.1 , grams/10 minutes                                                                    0.92    0.44                                     Melt index, MF.sub.10, grams/10 minutes                                                                    38      24                                       Flow rate ratio, MF.sub.10 /MF.sub.1                                                                       41.4    54.5                                     Hexane extractables, weight percent                                                                        0.47    0.41                                     Oven volatiles content, weight percent                                                                     0.20    0.28                                     Stiffness, psig              165,000 160,000                                  Molecular Weight Parameters, GPC                                              Molecular weight distribution,  --Mw/ --Mn                                                                 7.6     10.5                                     Tensile Properties                                                            Tensile strength at yield, psig at 2 inches/minute                                                         4540    4600                                     Tensile strength at ultimate, psig at 2 inches/minute                                                      3410    2810                                     Elongation at yield, percent at 2 inches/minute                                                            10      11                                       Elongation at ultimate, percent at 2 inches/minute                                                         1200    689                                      Impact Properties                                                             Tensile impact strength, ft-lb/in.sup.2                                                                    65      88                                       Izod impact strength, ft-lb/in notch                                                                       9.2     9.8                                      Thermal Properties                                                            Vicat softening point, ° F                                                                          266     262                                      Brittleness temperature, ° C                                                                        --      --                                       __________________________________________________________________________     .sup. (1) Triethylaluminum/catalyst weight ratio = 2.6/1 to 3.75/1.      

                  TABLE II                                                        ______________________________________                                        Conditions: 160° F, 300 psig, 34 mol percent H.sub.2,                  13/1 to 14/1 triethylaluminum/catalyst weight ratio                                              RUN A   RUN B                                              Cut number           5R     8R     10R                                        ______________________________________                                        Total polymer produced, grams                                                                      3628   5509   6637 1952                                  Inventory turnover (No. of times)                                                                  3.0    4.6    5.5  1.6                                   Percent original inventory remaining                                                               5      1      0.4  20                                    Bulk density, grams/cubic centimeter                                                               0.36   0.37   0.37 0.41                                  MF.sub.10            28.7   38.7   48.2                                       MF.sub.1             0.89   1.0    1.3                                        MF.sub.10 /MF.sub.1  32.3   38.7   37.1                                       ______________________________________                                    

EXAMPLE II

A carbon steel reactor approximately 2 feet in diameter by 3.0 feet inlength was used in this continuous ethylene-propylene polymerization.Temperatures were 181° F at one end of the reactor, 171° F at the centerof the reactor and 181° F near the take-off barrier end and reactortotal pressure was 400 psig. Ethylene was fed to the reactor at 20.57pounds/hour and propylene was added at 0.29 pounds per hour. The recyclegas rate was 2.29 actual cubic feet per minute and the recycle quenchliquid, isopentane, rate was 0.29 gallons/minute. The supported titaniumcatalyst was added at about 0.3 grams per hour as a dilute slurry inisopentane. The amount of slurry added was about 3 gallons per hour.Triethylaluminum cocatalyst was added as a solution in isopentane at arate of 35 milliliters per hour at a concentration of 0.025 gramstriethylaluminum per milliliter.

Gas analyses of reactor recycle gases were continuously made and typicalvalues were: hydrogen, 37 mol percent; ethane, 0.3 mole percent;propene, 1.1 mol percent; isopentane, 1 mol percent and ethene, 60.6 molpercent.

The melt index of product was about 0.58 grams/10 minutes.

EXAMPLE III

Ethylene was polymerized in the same manner described in EXAMPLE I. Thecatalyst was 2.0 weight percent chromium trioxide on W. R. Grace #952SiO₂. Catalyst was calcined at 1200° F. with dry oxygen for 12 hours.Catalyst, triisobutylaluminum and ethylene were continuously charged tothe reactor at 210° F. under 300 psig. pressure. Hydrogen was charged asneeded to maintain 35 mol percent H₂ in the reactor. The mole ratio ofAl(i-Bu)₃ /CrO₃ was 3. The polymer yield based on catalyst was 4,600grams/gram. Polymer was removed continuously as a melt. The polymerproduced showed the following physical properties:

                  TABLE III                                                       ______________________________________                                                                    Wt.    Wt.                                                                    Percent                                                                              Percent                                                                Extract-                                                                             vol-                                       Cut  M.I.   MF.sub.10                                                                             MF.sub.10 /MF.sub.1                                                                   ables  atiles  --Mw/ --Mn                         ______________________________________                                        5    0.20   22.2    111     1.5    0.65   14.7                                6    0.12   16.6    138     1.6    0.87   17.0                                7    0.12   20.2    168     1.8    0.98   15.4                                ______________________________________                                    

EXAMPLE IV

Propylene was polymerized by an active titanium chloride catalyst withdiethylaluminum chloride cocatalyst continuously in the gas phase underconditions tabulated in Table IV. The propylene served as its own quenchliquid for heat removal. Polymer was intermittently removed asparticulate through a double ball-valved lock chamber attached to thetake-off end of the reactor.

                                      TABLE IV                                    __________________________________________________________________________    POLYMERIZATION OF PROPYLENE                                                   Catalyst: Titanium trichloride                                                Cocatalyst: Diethylaluminum chloride                                          Conditions: 160° F, 300 psig, 1 mole percent hydrogen                  Time on stream, minutes                                                                           145      270     153     225     162                      Type of catalyst addition                                                                         Batch    Batch   Continuous                                                                            Batch   Continuous               Et.sub.2 AlCl/TiCl.sub.3 ratio                                                                    2.8      2.8     3.0     2.8     2.9                      TiCl.sub.3 addition rate, milligrams/hour                                                         48.sup.(1)                                                                             24-48.sup.(2)                                                                          45     24-48.sup.(2)                                                                          46                      Total polymer produced, grams                                                                     165      486     296     358     300                      Polymer yield, grass/gram                                                                         (0-145 min) 1970                                                                       (0-270 min) 3120                                                                      (0-153 min) 2600                                                                      (0-225 min)                                                                           (0-162 min) 2040                             (0-60 min) 640                                                                         (0-60 min) 1225 (0-90 min) 172                                       (60-145 min) 4600                                                                      (60-120 min) 3800                                                                             (90-225 min) 7200                                             (120-180 min) 5300                                                            (180-240 min) 4700                                                            (240-270 min) 3000                               __________________________________________________________________________     .sup.(1) A 12 milligram portion of catalyst added every 15 minutes up to      90 minutes. No catalyst added after 90 minutes.                               .sup.(2) A 12 milligram portion of catalyst added every 15 minutes up to      90 minutes. A 12 milligram portion of catalyst added every 30 minutes fro     90 to 270 minutes.                                                       

EXAMPLE V

A supported titanium chloride catalyst and triethylaluminum catalystwere employed in the same manner as described in Example I usingapproximately 3 mol percent propylene in the reactor gas to copolymerizewith the ethylene. Liquid propylene was added continuously at the rateof 30 milliliters/hour which maintained its concentration at 3 molpercent in the reactor gas. Copolymer was removed by way of a doubleball-valved lock chamber attached to the take-off end of the reactor asparticulate. Catalyst and cocatalyst were deactivated by treating thecopolymer with 250° F. steam. A copolymer inhibitor package was addedand the product thereof was melt extruded in the normal manner to formproduct pellets. Conditions of two such runs are shown in Table V below.

                                      TABLE V                                     __________________________________________________________________________    Run period        1  2  3  4    5A 5B 6   7   8   9    10  11                 __________________________________________________________________________    Time on stream, hours, minutes                                                                  5,12                                                                             3  5,20                                                                             4,22 3,8                                                                              3,8                                                                              6,37                                                                              7,10                                                                              6,55                                                                              4,22 3,15                                                                              2,45               Temperature, ° F                                                                         179                                                                              178                                                                              179                                                                              177  178                                                                              178                                                                              180 182 186 185  207 207                Total pressure, psig                                                                            300                                                                              300                                                                              300                                                                              300  300                                                                              300                                                                              300 300 300 300  300 300                Ave. catalyst, feedrate, -milligrams/hour                                                       37.0                                                                             29.1                                                                             30.9                                                                             33.3 40.2                                                                             40.2                                                                             42  37  33.3                                                                              37.9 39.2                                                                              41.0               *TEA/CAT          7.5                                                                              7.5                                                                              7.5                                                                              7.5  7.5                                                                              15 7.5 7.5 7.5 15   15  7.5                Recycle gas composition, mol percent                                          Hydrogen          38 35 36 31   40 40 42  41  39  36   36  36                 Ethylene          52 44 52 61   48 48 41  46  50  55   52  52                 Ethane            6.6                                                                              20.5                                                                             7.8                                                                              4.2  8.6                                                                              8.6                                                                              12.6                                                                              8.8 7.0 5.1  8.3 8.3                Propylene         2.3                                                                              3.2                                                                              3.2                                                                              3.2  2.6                                                                              2.6                                                                              3.1 2.9 3.4 2.9  3.2 3.2                Isopentane        1  1  1  1    1  1  1   1   1   1    1   1                  Reactor bleedrate, cubic feet/hour                                                              0.87                                                                             0.86                                                                             0.59                                                                             0.61 0.69                                                                             0.69                                                                             0.63                                                                              0.64                                                                              0.63                                                                              0.62 0.59                                                                              0.59               Polymer produced, grams                                                                         500                                                                              690                                                                              822                                                                              1357 0  165                                                                              339 1416                                                                              1015                                                                              1764 754 348                Catalyst yield, gram/grams                                                                      2600                                                                             8000                                                                             4980                                                                             9320 0  620                                                                              1150                                                                              5345                                                                              4410                                                                              10,660                                                                             5915                                                                              3130               Melt index, grams/10 minutes                                                                    0.17                                                                             0.2                                                                              0.2                                                                              0.17-   -- --  6-7 6-7 6-7  6-7 6-7                                           1.0                                                Run period        1  2                                                        __________________________________________________________________________    Time on stream, hours, minutes                                                                  4,53                                                                             5,15                                                     Temperature, ° F                                                                         193                                                                              200                                                      Total pressure, psig                                                                            300                                                                              300                                                      Ave. cat. feedrate, milligrams/hour                                                             40 28                                                       TEA/CAT*          7.5                                                                              7.5                                                      Recycle gas comp., mol percent                                                Hydrogen          44 42                                                       Ethylene          45 46                                                       Ethane            7.0                                                                              8.0                                                      Propylene         2.9                                                                              2.95                                                     Isopentane        1  1                                                        Reactor bleedrate, cubic feet/hour                                                              0.62                                                                             0.67                                                     Polymer produced, grams                                                                         1055                                                                             1539                                                     Catalyst yield, grams/grams                                                                     5375                                                                             8800                                                     Melt index, grams/10 minutes                                                                    12-20                                                                            17-19                                                    __________________________________________________________________________     *TEA/CAT is the weight ratio of triethylaluminum to catalyst used.       

EXAMPLE VI

A supported titanium chloride catalyst and triethylaluminum cocatalystwere employed for the polymerization of ethene in the same manner asExample I. Polymer was removed by way of a double ball-valved lockchamber as particulate. Catalyst was deactivated by treating with steamat 250° F. Polymer inhibitor package was added and the result thereofwas melt extruded in the normal manner to form product pellets.Polymerization product conditions and properties of some of the variouscuts are shown below in Tables VI and VII.

                                      TABLE VI                                    __________________________________________________________________________    Polymerization Conditions                                                     Temperature, Zone 1 ° F                                                               180  160-205                                                                           160-205                                                                           160-205                                                                           160-205                                                                           205 190                                                                              195 195 185  190                                                                              190                Zone 2 ° F                                                                            175  160-205                                                                           160-205                                                                           160-205                                                                           160-205                                                                           205 189                                                                              192 190 182  186                                                                              190                Exit port ° F                                                                         165  170 170 170 170 170 173                                                                              175 172 170  174                                                                              170                Solvent reservoir                                                                            137  150 150 145 150 150 152                                                                              152 152 152  156                                                                              140                Pressure, psig 300  300 300 300 300 300 300                                                                              300 300 300  300                                                                              300                Reaction gas composition, mol %                                               Hydrogen       25   22  22  20  25  25  60 35  42  40   44 55                 Ethylene       74   77  77  79  73  72  39 64  56  59   55 41                 Ethane         0.2  0.3 0.3 0.2 0.4 0.9 0.3                                                                              0.6 0.6 0.4  3.0                                                                              0.4                Isopentane     1    1   1   1                                                 Reactor vent rate, cubit                                                                     0.67 0.67                                                                              0.67                                                                              1.92                                                                              1.05                                                                              0.20                                                                              0.65                                                                             0.72                                                                              0.77                                                                              0.75 0.80                                                                             0.72               feet/hour                                                                     Catalyst                                                                      Feeder conc., milligrams/liter                                                               125  125 62.5                                                                              62.5                                                                              62.5                                                                              62.5                                                                              62.5                                                                             125 80  62.5 31.2                                                                             40                 Feed rate, milligrams/hour                                                                   31.9 25.2                                                                              10.6                                                                              8.7 11.9                                                                              4.85                                                                              21.8                                                                             17.2                                                                              9.1 2.9  11.6                                                                             11.0               Cocatalyst                                                                    AlE.sub.3 feeder conc., milli-                                                grams/liter    1,250                                                                              1,250                                                                             625 625 625 625 625                                                                              1,250                                                                             800 625  313                                                                              200                AlEt.sub.3 feed rate, milli-                                                  grams/hour     319  252 106 87  119 485 218                                                                              172 91  29   116                                                                              55                 Weight ratio AlEt.sub.3 /catalyst                                                            10   10  10  10  10  10  10 10  10  10   7.5                                                                              5                  Total run time, hours                                                                        9.8  14.8                                                                              1.8 6.2 7.5 7.8 20.9                                                                             7.5 2.5 5.8  6.5                                                                              22.9               Total polymer produced, grams                                                                663  2,107                                                                             781 619 1,146                                                                             749 52 366 429 3,335                                                                              2.05                                                                             3077               Polymer yield on catalyst,                                                    grams/gram     2,000                                                                              5,660                                                                             41,700                                                                            11,600                                                                            12,800                                                                            19,700                                                                            -- 2.830                                                                             19,240                                                                            204,000                                                                            2,715                                                                            12,200             __________________________________________________________________________

                  TABLE VII                                                       ______________________________________                                                             Cuts   Cuts                                                                   13-22  23-39                                             ______________________________________                                        General Properties                                                            Annealed density, g/cc 0.9734   0.9787                                        Inherent viscosity, dl/g                                                                             1.99     1.28                                          Melt index, MF.sub.1, g/10 min                                                                       1.1      7.3                                           Melt index, MF.sub.10, g/10 min                                                                      35       234                                           Flow rate ratio, MF.sub.10 /MF.sub.1                                                                 32       32                                            Hexane extractables, wt %                                                                            0.30     0.70                                          Oven volatiles content, wt %                                                                         0.04     0.33                                          Stiffness, psig        137,000  179,000                                       Tensile Properties                                                            Tensile strength at yield, psig                                               at 2 in/min            4,520    --                                            Tensile strength at ultimate, psig                                            at 2 in/min            2,940    4,850                                         Elongation at yield, % at 2 in/min                                                                   11       --                                            Elongation at ultimate, % at 2 in/min                                                                1,100    9.9                                           Impact Properties                                                             Tensile impact strength, ft-lb/in.sup.2                                                              82       22                                            Izod impact strength, ft-lb/in.sup.2                                                                 9.7      0.55                                          Thermal Properties                                                            Vicat softening point, ° F                                                                    263      259                                           ______________________________________                                    

EXAMPLE VII

Propylene was polymerized in essentially the same manner described inEXAMPLE I. The recycle gas and quench liquid were propylene. The meltertemperature was 350° F. while the catalyst kill section operated at 400°F. An active titanium chloride catalyst (33 milligrams) withdiethylaluminum chloride cocatalyst (77 milligrams), mol ratio Al/Ti -3, was charged to the reactor every thirty minutes. Hydrogen was addedas needed to maintain 2.9 mol percent in the reactor gas cap. Thereactor temperature was maintained at 160° F. and the reactor pressurewas controlled at 300 psig by controlling temperature in the recyclecondenser at about 120° F. A polymer yield based on catalyst of 10,000grams/gram was obtained. The polymer was removed from the reactor as amelt. The polymer showed a melt flow rate of 16.4 grams/10 minutes at230° C. under a load of 2,060 g. The 68° C. n-hexane extractables was4.0 weight percent.

EXAMPLE VIII

Ethylene was polymerized in the same manner described in Example Iexcept in this case two sections of the reactor were maintained atdifferent temperatures. Reactor section one was operated at 160° F.while reactor section two was operated at 210° to 230° F. This wasaccomplished by varying the amount of isopentane quench added to eachsection. The catalyst used was a supported titanium compound and analuminum triethyl cocatalyst was added in a weight ratio of cocatalystto catalyst of three to one. The reactor pressure was controlled at 300psig. and the hydrogen concentration was maintained at 40 mol percent. Apolymer yield of 62,000 grams of polymer/gram of catalyst was obtained.The polymer melt index was measured at 5.5 with a MF₁₀ /MF₁ of about 40and a spiral flow of 18 inches. Polymer having the same M.I. made undersingle temperature conditions showed an MF₁₀ /MF₁ value of about 34 anddemonstrated a spiral flow of about 16 inches.

Spiral flow is an empirical method of assessing ease of processabilityof a polymer by measuring the length of flow in a special mold underspecific temperature and pressure conditions. The longer the spiral flowthe easier is the processability.

What is claimed is:
 1. Apparatus for the vapor phase polymerization ofat least one polymerizable monomer comprising:(a) a horizontal reactorof substantially circular cross-section containing a centrally-locateddrive shaft extending longitudinally through said reactor to which areattached a plurality of adjacently located paddles, which paddles causeessentially no forward or backward movement of the particulate mattercontained in said reactor and extend transversely within and to a shortdistance from the internal surfaces of said reactor, said reactor beingdivided into two or more individuallypolymerization-temperature-controllable polymerization sections by oneor more barriers so constructed to allow free reactor gas mixing in saidreactor and to control movement of said particulate matter between saidsections; (b) driving means for said drive shaft; (c) One or morereactor off-gas outlets spaced along the topward part of said reactor;(d) one or more vapor recycle inlets spaced along the bottomward part ofsaid reactor; (e) one or more catalyst addition inlets spaced along saidreactor; (f) a plurality of quench liquid inlets spaced along thetopward part of said reactor whereby quench liquid can be introducedinto said two or more sections of said reactor; and (g) take-off meansfor said particulate matter at one end of said reactor.
 2. The apparatusof claim 1 wherein each of said polymerization sections contains one ormore said reactor off-gas outlets, one or more of said vapor recycleinlets and one or more of said catalyst addition inlets.
 3. Theapparatus of claim 1 wherein said take-off means is:(1) a thin barrierfilling the cross-sectional area of said reactor and situated near oneend of said reactor which contains an aperture so constructed to allowpassage of reactor gases and controlled movement of said particulatematter in the direction of take-off, (2) a take-off zone contained insaid reactor adjacent to said barrier in the direction of take-off whichcontains at least one impellor, and (3) an opening in said take-off zonewhereby said particulate matter can be removed from said reactor withoutsubstantial pressure letdown.
 4. The apparatus of claim 2 wherein saidtake-off means is:(1) a thin barrier filling the cross-sectional area ofsaid reactor and situated near one end of said reactor which contains anaperture so constructed to allow passage of reactor gases and controlledmovement of said particulate matter in the direction of take-off, (2) atake-off zone contained in said reactor adjacent to said barrier in thedirection of take-off which contains at least one impellor, and (3) anopening in said take-off zone whereby said particulate matter can beremoved from said reactor without substantial pressure letdown.
 5. Theapparatus of claim 2 wherein said paddles are flat and arranged inimpellors, each of said impellors containing two paddles and circularlyoff-set from the next adjacent impellor or impellors.
 6. The apparatusof claim 3 wherein said paddles are flat and arranged in impellors, eachof said impellors containing two paddles and circularly off-set from thenext adjacent impellor or impellors.
 7. The apparatus of claim 4 whereinsaid paddles are flat and arranged in impellors, each of said impellorscontaining two paddles and circularly off-set from the next adjacentimpellor or impellors.
 8. Apparatus for the vapor phase polymerizationof at least one polymerizable monomer comprising:(a) a horizontalreactor of substantially circular cross-section containing acentrally-located drive shaft extending longitudinally through saidreactor to which are attached a plurality of adjacently locatedimpellors, each impellor being composed of two flat paddles and soarranged that the next adjacent impellor or impellors is circularlyoff-set, which paddles extend transversely within and to a shortdistance from the internal surfaces of said reactor, said reactor beingdivided into four individually polymerization-temperature-controllablepolymerization sections by three barriers so constructed to allow freereactor gas mixing within said reactor and control movement of saidparticulate matter between said sections; (b) driving means for saiddrive shaft; (c) at least one reactor off-gas outlet for each of saidsections spaced along the topward part of said reactor; (d) at least onevapor recycle inlet for each of said sections spaced along thebottomward part of said reactor; (e) at least one catalyst additioninlet for each of said sections spaced along said reactor; (f) aplurality of quench liquid inlets spaced along the topward part of saidreactor whereby quench liquid can be introduced into each of saidsections; and (g) take-off means for said particulate matter at one endof said reactor which is(1) a thin barrier filling the cross-sectionalarea of said reactor and situated near one end of said reactor whichcontains an aperture so constructed to allow passage of reactor gasesand controlled movement of said particulate matter in the direction oftake-off, (2) a take-off zone contained in said reactor adjacent to saidbarrier in the direction of take-off which contains one or more of saidimpellors, and (3) an opening in said take-off zone whereby saidparticulate matter can be removed from said reactor without substantialpressure letdown.